FIG. 13 is a conceptual diagram illustrating conventional moving body device 7. Acoustic device 6 includes controller 1, amplifier 2, and capacitor 3. Speaker 4 is electrically connected to an output side of acoustic device 6. Acoustic device 6 is mounted to moving body device 7.
Upon receiving a vehicle signal, controller 1 outputs an audio signal. Amplifier 2 amplifies the audio signal. An output from amplifier 2 is supplied to speaker 4 via capacitor 3. Capacitor 3 cuts a direct-current (DC) voltage in the output from amplifier 2. In the above configuration, acoustic device 6 starts to output sound 8 from speaker 4, based on the vehicle signal, at substantially the same time when moving body device 7 starts to move.
Patent Literature 1, for example, is known as citation relating to the invention of this application.